Anoxic Corrosion Behavior of Pipeline Steel in Acidic Soils

Acidic red soils are highly corrosive toward carbon steel, but the corrosive nature of this particular soil has not been well documented. Electrochemical techniques including Tafel plots, electrochemical impedance spectroscopy, and weigh loss test were used to characterize the properties and nature of pipeline corrosion in a typical acidic red soil at different water content values. The results show that corrosion rate and type and intensity of corrosion attack are significantly dependent on the soil water content and hence the soil moisture droplet or film absorbed on the steel surface. The corrosion rate increases with the water content up to ca. 30% soil water content (100% water-holding capacity), and it decreases with further increases in water content in the long-term test. The evolution of a kinetic parameter and a Fe oxide facilitating corrosion mechanism is proposed and discussed for the anaerobic corrosion of steel in acidic soils.